An objective of transcutaneous neurostimulation is to focus an adequate electrical energy concentration at a relatively small, preferred treatment location on the skin. The preferred treatment locations are typically locations such as nerve branches, trigger points, and acupuncture points, and are evidenced as points of lower relative impedance.
One approach to determine the location of low relative impedance points is to use an array of electrodes where the pairs of alternating polarity are individually addressable. This method is employed by Bijelic in U.S. Patent Application Serial No. 2008/0027507. An operator can then step through the combinations of electrodes, scanning for low relative impedance values. After the low impedance points are identified, the operator must use another device to treat the identified areas. The process of scanning and treating must be repeated to accomplish the desired results. Performing this approach, either manually or in an automated fashion, is time-consuming and costly.
Other prior devices and methods do not address the problem. For example, in U.S. Pat. No. 4,238,726, Ichijo discusses a method of determining points of low impedance electrically without mentioning using an electrode configuration as a means. Molina-Negro et al., in U.S. Pat. No. 4,541,432, discuss using a waveform to treat pain without regard to the electrode configuration. Matos, in U.S. Patent Application Serial No. 2003/0233129, discusses a method of scanning and stimulating without regard to relative electrode size and spacing.
Another common method of locating low impedance points is to use a configuration of concentric electrodes. An outer electrode has a substantially larger area than a smaller, inner “treatment” electrode. The area ratio of the outer electrode to the inner electrode is typically between 1.2/1 and 5.0/1, and the spacing between the electrodes is controlled at a small dimension, which is typically less than 0.40 inches.
By measuring and noting the impedance measurements between the inner and outer electrodes, as the electrode pair is moved over the body, one can locate points of low impedance and, thus, preferred treatment locations. This is discussed generally by Colthurst in U.S. Pat. No. 7,483,734.
Axelgaard, in U.S. Pat. No. 6,038,485, discusses controlling current distribution and directing electrical pulses via rows and columns of electrodes. Axelgaard addresses spacing and area of individual electrodes but does not disclose anything but equal spacing and equal electrode areas. Schumann, in U.S. Patent Application Serial No. 2007/0106342, discusses a means of scanning and locating trigger points and mentions a relationship between spacing and skin conductance. However, Schumann does not teach anything about having different areas of electrodes in combination with particular spacing between the electrodes. Schumann also discusses “chasing the pain” via multiple cycles of scanning and treating. Also worth noting is that Bijelic, in U.S. Patent Application Serial No. 2008/0027507, discusses arrays of electrodes with a single spacing and single dimension.